Complement amplifies TLR4-dependent transcripts and caspase-11–dependent cell death in macrophages. WT, C3aR KO, and C3 KO RAW cell lines were treated with LPS for 2 h and relative expression of (A) caspase-11 or (B) il-6 and tnf was calculated via qRT-PCR, compared with GAPDH expression. Indicated cell lines were treated with CTB/LPS for 16 h and (C) cytotoxicity was measured or (D) supernatants and cell lysates were collected for Western blot analysis of indicated proteins. (E) WT (control [WT] or C3aR-antagonist treated [C3aR-Ant]), caspase-11–deficient (Casp11^−/−), C3aR-deficient (C3aR^−/−), and C3-deficient (C3^−/−) primary BM-derived macrophages (BMDMs) were treated with CTB/LPS for 16 h and cytotoxicity was measured. Indicated BMDMs were treated with LPS for 2 h and the relative expression of (F) caspase-11 or (G) il-6 and tnf was calculated via qRT-PCR, compared with GAPDH expression or (H) analyzed for release of IL-6 and TNF via ELISA. All cytotoxicity was measured by release of LDH. Statistics analyzed via the unpaired Student’s t test. *, P < 0.05; **, P < 0.01; ***, P < 0.001. Data are representative of at least three independent experiments (A–H), with three technical replicates each time.